Recent Advances in Geo-, Paleo- and Rock- Magnetism

Editorial Board (March 2021)
Editor-in-Chief
Takeshi Sagiya, Nagoya University, Japan

Vice Editors-in-Chief
Masahito Nosé, Nagoya University, Japan

Aitaro Kato, University of Tokyo, Japan

Editors
Hideo Aochi
Pascal Audet
Kiyoshi Baba
Joseph B.H. Baker
Nanan Balan
Stephan Christoph Buchert
Sonia CalvariPeter Chi
Harold C. Connolly Jr
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Hao Dong
Guangyu Fu
Hidenori Genda
Aditya Gusman
Tomasz Hadaś
Shin-Chan Han
Stuart Henrys
James Hickey
Hauke Hussmann

Mie Ichihara
Takeo Ito
Hidekatsu Jin
Art Jolly
Shunichi Kamata
Nobuki Kame
Yoko Kebukawa
Kunihiro Keika
Tomokazu Kobayashi
Kostas Konstantinou
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Atsuko Namiki
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Tatsuhiko Saito
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Yih-Min Wu
Chuang Xuan
Takahiro Yamamoto
Yuhji Yamamoto
Tadashi Yamasaki
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Kazunori Yoshizawa
Yohei Yukutake
Seiji Zenitani

Hiroo Kanamori
Jun'ichiro Kawaguchi
Takafumi Matsui
Hitoshi Mizutani

Toshitaka Tsuda
Zhongliang Wu
Kiyoshi Yomogida

Advisory Board
Benjamin Fong Chao
Bernard Chouet
Yoshimori Honkura
Toshihiko Iyemori

Journal Scope
Earth, Planets and Space (EPS) is the official journal of Society of Geomagnetism and Earth, Planetary
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EPS is a peer-reviewed, open-access journal published under SpringerOpen. It is an international journal
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Earth, Planets and Space(2019) 71:68
Tarduno et al. Earth, Planets and Space
https://doi.org/10.1186/s40623-019-1043-5

Open Access

PREFACESpecial issue “Recent advances in geo-,
paleo- and rock-magnetism”
John A. Tarduno1,2*, Hirokuni Oda3, Yuhji Yamamoto4, Chuang Xuan5, Ioan Lascu6 and Koji Fukuma7

loess and paleosol paleomagnetic records of Brunhes
geomagnetic excursions from Central Asia. In particular,
they highlight recordings of the Blake and Laschamp geomagnetic excursions.
Global records of the archeomagnetic field and excursions are of crucial importance not only for understanding the past magnetic field but also for providing context
on modern changes. Specifically, there is a debate overwhat excursions tell us about the rapidly diminishingmodern dipole field; some analyses of the rate of intensity changes support the idea of an impending reversal
or excursion, whereas others argue that the geomagnetic
field patterns during recent excursions differ from thoseof the present-day field. The latter interpretation is highly
dependent on the nature of global data coverage. Endeavors of the type defined by Kitahara et al. (2018), Ahn et al.
(2018) and Li et al. (2018) can move us closer to global
coverage; they are crucial for improving predictions of
the future magnetic field and our planetary magnetic
shield.
In a Frontier Letter, Kato et al. (2018) present paleointensity results from single silicate crystals separated from
Cretaceous granites of Japan. They yield data from plagioclase feldspars that bear on the ongoing debate overthe field during Superchrons, periods tens of millionsof years long with few (or no) geomagnetic reversals.
Numerical simulations, theory and prior paleointensity
data from single feldspars argue for a strong field during
the Cretaceous Normal Superchron and an inverse relationship between geomagnetic reversal frequency andfield strength. However, results from whole rocks fail toshow this relationship. The results of Kato et al. (2018)not only highlight the potential of single silicate crystal
studies, but also strongly support a high field during theCretaceous Normal Superchron, representing a major
contribution to this fundamental issue.

The special issue of Earth, Planets and Space “Recent
Advances in Geo-, Paleo- and Rock-Magnetism” wasmotivated by presentations given in Session S-EM18“General Contributions in Geomagnetism, Paleomagnetism, and Rock magnetism” held during the Japan Geoscience Union–American Geophysical Union (JpGU–
AGU) 2017 Joint Meeting (20–25 May in Chiba, Japan).
Contributions span the broad range of topical developments in Earth magnetism including the disciplines ofarcheomagnetism, paleomagnetism, paleointensity, rockmagnetism, crustal magnetism and biogeomagnetism. In
addition, several contributions present advances in methods of analysis. These areas are briefly introduced below
with an emphasis on the advances represented, current
community debates and the motivation the new results
provide for further study.

Archeomagnetism and paleomagnetism
Contributions in archeomagnetism and paleomagnetism
display the continual advances in the collection of new
data recording the history of the geomagnetic field.
Kitahara et al. (2018) present Tsunakawa–Shaw paleointensity estimates from a tenth-century kiln from Japanthat further demonstrate the viability of this protocol
for defining field strength from archeological materials.
The field intensity values derived are somewhat lower
values than those reported in prior studies in Japan; thisshould provide motivation for further investigation. Ahn
et al. (2018) discuss the potential of sediments from Jeju
Island, Korea, for recording young (17–22 kyr) excursions and the challenges of distinguishing these considering rock magnetic complexities. Li et al. (2018) discuss*Correspondence: john@earth.rochester.edu
1
Department of Earth and Environmental Sciences, Universityof Rochester, Rochester, NY 14627, USA
Full list of author information is available at the end of the article© The Author(s) 2019. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License(http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium,provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license,
and indicate if changes were made.

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Rock magnetism
Rock magnetism describes the basic physics of rockand mineral magnetic recorders and as such underpins
our understanding of paleomagnetism. The Verweytransition, the change from cubic to monoclinic crystal
structure in magnetite at 120 K, continues to be a focus
of interest in the community. Lindquist et al. (2019) use
transmission electron microscope imaging to document domain wall motion across the Verwey transition in a magnetite sample deformed in the laboratory.
These authors relate these data to the role stress, anddislocations can play in controlling magnetic properties. In contrast, Dunlop and Özdemir (2018) study
magnetite annealed to remove the effects of stress.
Their rock magnetic data on size-controlled magnetite allow them to study the degree to which remanence
memory occurs when cycling across the transition.
While the authors conclude that the results are still too
scattered to be useful for magnetic granulometry, theseresults together with the observations of Lindquist
et al. (2019) further define the phenomenology of the
Verwey transition and may eventually lead to a better
understanding of other observations such as magnetic
field controls on low-temperature magnetic properties.

Marine geology/geophysics
From the earliest definition of the marine magnetic
anomalies that were crucial for the plate tectonics scientific revolution, magnetic investigations have been
central in marine geology and geophysics. Today there
remain unknowns about seafloor magnetization processes. Studies addressing these unknowns take on evengreater importance as we look for terrestrial analogs
for hydrothermal processes on other planets and satellites. Fujii et al. (2018) discuss the fundamental hydrothermal alteration effects on the magnetic properties ofsubmarine basalts from the Okinawa Trough. Although
their data cannot completely exclude effects of alteration-induced self-reversal by ionic recording, available
geochemical constraints support a conversion of highmagnetic titanomagnetites to non-magnetic phases. Fujii
and Okino (2018) combine magnetic mapping with submersible photographic documentation and sampling
to study off-axis lava flows of the Central Indian Ridge
near hydrothermal fields. This diverse data set allows theauthors to draw inferences on the emplacement of altered
and less magnetic material versus more highly magnetized recently erupted flows.
Global magnetic field studies and applications
A plethora of new satellite data offer opportunities foranalyses of tectonic structure, magnetic anomalies andseismicity. Lei et al. (2018) identify a possible correlation between the vertical component of the lithosphericmagnetic field and continental seismicity in Mainland
China and surrounding areas and discuss this in terms oflithospheric viscosity and temperature gradients. Rogeret al. (2019) discuss the investigation of core flow using
Slepian functions. Although the authors conclude that
more work is needed to address spectral leakage, potential remains to study features of core flow, including thepotential influence of unusual core–mantle features suchas large low-shear-velocity provinces that have been proposed to be long-term sites of flux expulsion affecting themost recent and paleofield of the South Atlantic Anomaly region.

Biogeomagnetism
Biogeomagnetism is an expanding field and one inwhich many discoveries await further research. In an
Express Letter, Oda et al. (2018) offer one such discovery. The authors report the first identification of magnetofossils of magnetotactic bacteria in ferromanganesecrust from the Pacific Ocean. The report of this occurrence is surprising and has far-reaching implications.
Bacterial magnetite has long been known to be concentrated at the modern redox boundary in pelagic sediments (e.g., studies of the Ontong Java Plateau of theWestern Pacific Ocean). The observations of Oda et al.
(2018), however, reveal that one should not assume thatseemingly fully oxic deep-sea ferromanganese crusts
are devoid of magnetotactic bacteria. This should
motivate studies to define paleomicroenvironments inthese crusts. Moreover, these new observations suggest a greater role of ferromanganese crusts and related
deposits for global iron cycling. In a Frontier Letter,
Zhang and Pan (2018) review the characterization ofmagnetite associated with magnetoferritins and magnetotactic bacteria. The former relates to important
potential biomedical applications, whereas the latter
applies to the continued effort to define modern magnetotactic bacteria populations and magnetofossils indeep geologic time.

Methods
Retrieving pristine rock magnetic and paleomagnetic
records from natural samples remains challenging, especially as the discipline seeks records with ever greater
spatial and temporal resolution. A number of contributions address advances in techniques of sample preparation and/or data analysis.
Myre et al. (2019) present applications of a fast spatial
domain algorithm “TNT-NN” to address the inversion ofdata sets from scanning SQUID magnetometers (SSMs).

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Tarduno et al. Earth, Planets and Space(2019) 71:68

Page 3 of 3

As opposed to ultrasensitive three-component SQUID
magnetometers, these magnetometers directly measure
only the vertical component on the magnetization, andtherefore, the other components must be inferred by aninversion of the data with associated uncertainties. The
work of Myre et al. (2019) is an important step forward inproviding a robust framework for the analyses of SSM data.
Analyses of data derived from continuous measurements of sedimentary cores using pass-through SQUID
magnetometers have also been a target of software development. Yamamoto et al. (2018) present a successful application of a software UDECON (Xuan and Oda 2015) todeconvolve natural remanent magnetization data obtained
from such continuous measurements spanning a geomagnetic reversal; tests show that the software can help extract
fine-scale features in the data which are in good agreementwith discrete paleomagnetic sample measurements.
In technical reports, Hatakeyama (2018) present online
plotting options for viewing paleomagnetic and rock magnetic data assisting international collaborations, whereas
Anai et al. (2018) discuss a reductive chemical demagnetization approach with the promise of being able to remove
secondary minerals and their magnetizations reveals primary recordings of the geomagnetic field from reef limestones and potentially other rock types.
The rock magnetic study of single silicate grains has
mainly focused on their use in paleointensity or paleodirections, but their use in provenance studies has only recently
been recognized. Usui et al. (2018) present methods ofseparation and present the first rock magnetic results fromquartz and feldspar derived from red clays, presenting theirresults as a new provenance indicator. Given the areal distribution of red clays, this work opens many new possibilities for future investigations.

References
Ahn H‑S, Sohn YK, Lee J‑Y, Kim JC (2018) Preliminary paleomagnetic androck magnetic results from 17 to 22 ka sediment of Jeju Island, Korea:
Geomagnetic excursional behavior or rock magnetic anomalies? Earth
Planets Space 70:78. https://doi.org/10.1186/s40623‑018‑0850‑4
Anai C, Mochizuki N, Shibuya H (2018) Reductive chemical demagnetization: a
new approach to magnetic cleaning and a case study of reef limestones.
Earth Planets Space 70:184. https://doi.org/10.1186/s40623‑018‑0954‑x
Dunlop DJ, Özdemir Ö (2018) Remanence cycling of 0.6–135 µm magnetites
across the Verwey transition. Earth Planets Space 70:164. https://doi.
org/10.1186/s40623‑018‑0928‑z
Fujii M, Okino K (2018) Near‑seafloor magnetic mapping of off‑axis lava flows
near the Kairei and Yokoniwa hydrothermal vent fields in the Central
Indian Ridge. Earth Planets Space 70:188. https://doi.org/10.1186/s4062
3‑018‑0959‑5
Fujii M, Sato H, Togawa E, Shimadaand K, Ishibashi J (2018) Seafloor hydrother‑
mal alteration affecting magnetic properties of abyssal basaltic rocks:
insights from back‑arc lavas of the Okinawa Trough. Earth Planets Space70:196. https://doi.org/10.1186/s40623‑018‑0958‑6
Hatakeyama T (2018) Online plotting applications for paleomagnetic and rockmagnetic data. Earth Planets Space 70:139. https://doi.org/10.1186/s4062
3‑018‑0906‑5
Kato C, Sato M, Yamamoto Y, Tsunakawa H, Kirschvink JL (2018) Paleomag‑
netic studies on single crystals separated from the middle Cretaceous
Iritono granite. Earth Planets Space 70:176. https://doi.org/10.1186/s4062
3‑018‑0945‑yKitahara Y, Yamamoto Y, Ohno M, Kuwahara Y, Kameda S, Hatakeyama T (2018)
Archeointensity estimates of a tenth‑century kiln: first application of the
Tsunakawa–Shaw paleointensity method to archeological relics. Earth
Planets Space 70:79. https://doi.org/10.1186/s40623‑018‑0841‑5
Lei Y, Jiao L, Chen H (2018) Possible correlation between the vertical com‑ponent of lithospheric magnetic field and continental seismicity. Earth
Planets Space 70:179. https://doi.org/10.1186/s40623‑018‑0949‑7
Li G, Xia D, Appel E, Wang Y, Jia J, Yang X (2018) A paleomagnetic record inloess–paleosol sequences since late Pleistocene in the arid Central Asia.
Earth Planets Space 70:44. https://doi.org/10.1186/s40623‑018‑0814‑8
Lindquist AK, Feinberg JM, Harrison RJ, Loudon JC, Newell AJ (2019) The
effects of dislocations on crystallographic twins and domain wall motion
in magnetite at the Verwey transition. Earth Planets Space 71:5. https://doi.org/10.1186/s40623‑018‑0981‑7
Myre JM, Lascu I, Lima EA, Feinberg JM, Saar MO, Weiss BP (2019) Using TNT‑NN
to unlock the fast full spatial inversion of large magnetic microscopy data
sets. Earth Planets Space 71:14. https://doi.org/10.1186/s40623‑019‑0988‑8
Oda H, Nakasato Y, Usui A (2018) Characterization of marine ferromanganesecrust from the Pacific using residues of selective chemical leaching:identification of fossil magnetotactic bacteria with FE‑SEM and rockmagnetic methods. Earth Planets Space 70:165. https://doi.org/10.1186/
s40623‑018‑0924‑3
Roger HF, Beggan CD, Whaler KA (2019) Investigation of regional variation incore flow models using spherical Slepian functions. Earth Planets Space
71:19. https://doi.org/10.1186/s40623‑019‑0997‑7
Usui Y, Shimono T, Yamazaki T (2018) Rock magnetism of quartz and feldspars
chemically separated from pelagic red clay: a new approach to prov‑
enance study. Earth Planets Space 70:153. https://doi.org/10.1186/s4062
3‑018‑0918‑1
Xuan C, Oda H (2015) UDECON: deconvolution optimization software forrestoring high‑resolution records from pass‑through paleomagnetic
measurements. Earth Planets Space 67:183. https://doi.org/10.1186/
s40623‑015‑0332‑x
Yamamoto Y, Yamazaki T, Kanamatsu T (2018) An initial case study to decon‑
volve natural remanent magnetization of a continuous paleomagnetic
sample using the software UDECON. Earth Planets Space 70:160. https://doi.org/10.1186/s40623‑018‑0931‑4
Zhang T, Pan Y (2018) Constraining the magnetic properties of ultrafine‑ andfine‑grained biogenic magnetite. Earth Planets Space 70:206. https://doi.
org/10.1186/s40623‑018‑0978‑2

Authors’ contributions
All authors served as guest editors for this special issue. Lead guest editor John
Tarduno drafted the preface which was edited and approved by all authors. All
authors read and approved the final manuscript.
Competing interests
The authors declare that they have no competing interests.
Author details
1
Department of Earth and Environmental Sciences, University of Rochester,Rochester, NY 14627, USA. 2 Department of Physics and Astronomy, Universityof Rochester, Rochester, NY 14627, USA. 3 Geological Survey of Japan, National
Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki
305‑8567, Japan. 4 Center for Advanced Marine Core Research, Kochi Univer‑sity, Nankoku, Kochi 783‑8502, Japan. 5 School of Ocean and Earth Science,
National Oceanography Centre Southampton, University of Southampton,
Southampton SO14 3ZH, UK. 6 Department of Mineral Sciences, Smithsonian
Institution, National Museum of Natural History, Washington, DC 20560, USA.
7
Department of Environmental Systems Science, Doshisha University, Kyoto,
Japan.

Publisher’s Note

Received: 22 May 2019 Accepted: 24 May 2019

Springer Nature remains neutral with regard to jurisdictional claims in pub‑lished maps and institutional affiliations.

3

Recent Advances in Geo-, Paleo- and Rock- Magnetism

FRONTIER LETTER

Open Access

Paleomagnetic studies on single crystals separated fromthe middle Cretaceous Iritono granite
Chie Kato*, Masahiko Sato, Yuhji Yamamoto, Hideo Tsunakawa and Joseph L. Kirschvink
Earth, Planets and Space 2018, 70:176 DOI: 10.1186/s40623-018-0945-y
Received: 3 July 2018, Accepted: 25 October 2018, Published: 13 November 2018

Abstract

Paleointensity (µT)

Investigations of superchrons are the key to understanding long-term changes of the geodynamo and the mantle’s controlling role.
Granitic rocks could be good recorders of deep-time geomagnetic field behavior, but paleomagnetic measurements on whole-rockgranitic samples are often disturbed by alterations like weathering, and the presence of multi-domain magnetite. To avoid suchdifficulties and test the usefulness of single silicate crystal paleomagnetism, here we report rock-magnetic and paleomagnetic
properties of single crystals and compare those to the host granitic rock. We studied individual zircon, quartz and plagioclase crystals
separated from the middle Cretaceous Iritono granite, for which past studies have provided tight constraints on the paleomagnetismand paleointensity. The occurrence of magnetite was very low in zircon and quartz. On the other hand, the plagioclase crystals
contained substantial amounts of fine-grained single-domain to pseudo-single-domain magnetite. Microscopic features anddistinctive magnetic behavior of plagioclase crystals indicate that the magnetite inclusions were generated by exsolution. We
therefore performed paleointensity experiments by the Tsunakawa–Shaw method on 17
100
plagioclase crystals. Nine samples passed the standard selection criteria for reliablepaleointensity determinations, and the mean value obtained was consistent with the80
whole-rockpreviously reported whole-rock paleointensity value. The virtual dipole moment was
mean
22
2
estimated to be higher than 8.9 ± 1.8 × 10 Am , suggesting that the time-averaged field
60
strength during middle of the Cretaceous normal superchron was several times as large ascompared to that of non-superchron periods. Single plagioclase crystals which have40
plagioclase
exsolved magnetite inclusions can be more suitable for identification of magnetic signals
mean
single plagioclase crystal
and interpretation of paleomagnetic records than the conventional whole-rock samples or20
other silicate grains.

Keywords: Paleointensity, Granite, Single crystals, Feldspar, Zircon

0Graphical abstract*Corresponding author: Chie Kato, chiekato15@gmail.com

FRONTIER LETTER

Open Access

Constraining the magnetic properties of ultrafine- andfine-grained biogenic magnetite
Tongwei Zhang and Yongxin Pan*
Earth, Planets and Space 2018, 70:206 DOI: 10.1186/s40623-018-0978-2
Received: 2 September 2018, Accepted: 14 December 2018, Published: 24 December 2018

Abstract
Four samples containing ultrafine- and fine-grained magnetite of magnetoferritins and magnetotactic bacteria cells were magneticallycharacterized at both room and low temperatures. Transmission electron microscopy analysis showed that the biometrically synthesizedmagnetoferritins (M-HFn) have magnetite cores with a mean size of 5.3 ± 1.2 nm inside protein shells, while Magnetospirillum gryphiswaldense
MSR-1 cell produced intracellular magnetosome magnetites have a mean size of 29.6 ± 7.6 nm, arranged in a single chain. A pure M-HFn sample(M1), MSR-1 whole cell sample (M4) and two samples (M2, M3) mixing M-HFn with MSR-1 whole cells in different weight percentages were
measured, including hysteresis, temperature dependency of magnetization and remanence and frequency dependence of AC susceptibility at
low temperature. At room temperature, the ultrafine-grained magnetite core of M-HFn of M1 sample has a typical superparamagnetic (SP)behavior. The chain-arranged magnetosome magnetite of MSR-1 cells of M4 sample shows a stable single-domain (SD) state. At low temperature,
the M2 sample with ~ 16 wt% SD magnetosome magnetite and the M3 sample
with ~ 43 wt% SD magnetosome magnetite behave somewhat similar to the M1(pure M-HFn), due to the SP component from M-HFn magnetite. With thedominance of SP magnetite in samples M1, M2, and M3, the coercivity andsaturation remanence decrease significantly as temperature increasing from 5
to 20 K. Of note, the magnetization and frequency dependence of AC
susceptibility at low temperature are sensitive to SP magnetites in measured
samples. The magnetosome magnetite produced by MSR-1 has a Verweytransition temperature at around 100 K, which is consistent with previous
observations on magnetotactic bacteria. This study provides useful clues for
identification of SP and SD magnetite in sediments, as well as related potential
biomedical and biomagnetic applications.

Keywords: Superparamagnetism (SP), Magnetoferritins, Magnetosome

magnetite, Low-temperature measurements, Biogenic magnetite*Corresponding author: Yongxin Pan , yxpan@mail.iggcas.ac.cn
4Graphical abstract

Earth, Planets and Space

FULL PAPER

Open AccessA paleomagnetic record in loess–paleosol sequences sincelate Pleistocene in the arid Central Asia
Guanhua Li*, Dunsheng Xia, Erwin Appel, Youjun Wang, Jia Jia and Xiaoqiang Yang
Earth, Planets and Space 2018, 70:44 DOI: 10.1186/s40623-018-0814-8
Received: 5 January 2018, Accepted: 7 March 2018, Published: 19 March 2018

Abstract
Geomagnetic excursions during Brunhes epoch have been brought to the forefront topic in paleomagnetic study, as they provide key
information about Earth’s interior dynamics and could serve as another tool for stratigraphic correlation among different lithology.
Loess–paleosol sequences provide good archives for decoding geomagnetic excursions. However, the detailed pattern of theseexcursions was not sufficiently clarified due to pedogenic influence. In this study, paleomagnetic
analysis was performed in loess–paleosol sequences on the northern piedmont of the Tianshan
Mountains (northwestern China). By radiocarbon and luminance dating, the loess section waschronologically constrained to mainly the last c.130 ka, a period when several distinct
geomagnetic excursions were involved. The rock magnetic properties in this loess section are
dominated by magnetite and maghemite in a pseudo-single-domain state. The rock magnetic
properties and magnetic anisotropy indicate weakly pedogenic influence for magnetic record.
The stable component of remanent magnetization derived from thermal demagnetization
revealed the presence of two intervals of directional anomalies with corresponding intensity
lows in the Brunhes epoch. The age control in the key layers indicates these anomalies are likely
associated with the Laschamp and Blake excursions, respectively. In addition, relative
paleointensity in the loess section is basically compatible with other regional and global relative
paleointensity records and indicates two low-paleointensity zones, possibly corresponding to
the Blake and Laschamp excursions, respectively. As a result, this study suggests that the loesssection may have the potential to record short-lived excursions, which largely reflect thevariation of dipole components in the global archives.

Keywords: Geomagnetic excursion, Blake excursion, Laschamp excursion, Relative
paleointensity, Loess, Arid Central Asia

Fig. 1*Corresponding author: Guanhua Li, ligh1986@gmail.com

FULL PAPER

Open Access

Preliminary paleomagnetic and rock magnetic results from17 to 22 ka sediment of Jeju Island, Korea: Geomagnetic
excursional behavior or rock magnetic anomalies?
Hyeon-Seon Ahn*, Young Kwan Sohn, Jin-Young Lee and Jin Cheul Kim
Earth, Planets and Space 2018, 70:78 DOI: 10.1186/s40623-018-0850-4
Received: 2 January 2018, Accepted: 25 April 2018, Published: 9 May 2018

Abstract
Paleomagnetic and rock magnetic investigations were performed on a 64-cm-thick section of nonmarine unconsolidated muddy sediment from theGosan Formation on Jeju Island, Korea. This sediment was recently dated to have been deposited between 22 and 17 kyr BP calibrated, with asedimentation rate of 13–25 cm/kyr, based on many radiocarbon ages. Interestingly, stepwise alternating field (AF) demagnetization revealed
characteristic natural remanent magnetizations with anomalous directions, manifested by marked deviations from the direction of today’s axial
dipole field, for some separate depth levels. On the other hand, stepwise thermal (TH) demagnetization showed more complex behavior, resulting in
the identification of multiple remanence components. For all TH-treated specimens, consistently two different
components are predominant: a low-temperature component unblocked below 240–320 °C entirely having
normal-polarity apparently within the secular variation range of the Brunhes Chron, and a high-temperaturecomponent with unblocking temperatures (Tubs) between 240–320 and 520–580 °C that have anomalous
directions, concentrated in the ~ 13–34-cm-depth interval (~ 17–19 ka in inferred age) and possibly below ~ 53
cm depth (before ~ 20 ka). Rock magnetic results also infer the dominance of low-coercivity magnetic particles
having ~ 300 and ~ 580 °C Curie temperature as remanence carriers, suggestive of (titano)maghemite and/or
Ti-rich titanomagnetite and magnetite (or Ti-poor titanomagnetite), respectively. A noteworthy finding is thatAF demagnetizations in this study often lead to incomplete separation of the two remanence components
possibly due to their strongly overlapping AF spectra. The unusual directions do not appear to result fromself-reversal remanences. Then, one interpretation is that the low-temperature components are attributable topost-depositional chemical remanences, associated possibly with the later formation of the mineral phasehaving Tub ~ 300 °C, whereas the high-temperature components are of primary detrital origin that survived
later chemical influence. Accordingly, the unusual directions might record geomagnetic instability withinthe ~ 17–22 ka period manifested by multiple excursional swings, partly associated with the Tianchi/Hilina Pali
excursion. However, further work is needed to verify this interpretation and distinguish it from alternative
explanations that invoke rock magnetic complexities as the cause of the unusual directions.

Keywords: Gosan formation, Jeju Island, Paleomagnetism, Rock (sediment) magnetism, Geomagnetic
instability, Tianchi excursion, Hilina Pali excursion, 17–22 ka period*Corresponding author: Hyeon-Seon Ahn, mitsuki_ahs@hotmail.com; hs.ahn@gnu.ac.kr
5

Fig. 1

Recent Advances in Geo-, Paleo- and Rock- Magnetism

FULL PAPER

Open AccessArcheointensity estimates of a tenth-century kiln:
first application of the Tsunakawa–Shaw paleointensity
method to archeological relics
Yu Kitahara*, Yuhji Yamamoto, Masao Ohno, Yoshihiro Kuwahara, Shuichi Kameda
and Tadahiro Hatakeyama
Earth, Planets and Space 2018, 70:79 DOI: 10.1186/s40623-018-0841-5
Received: 3 January 2018, Accepted: 14 April 2018, Published: 9 May 2018

Abstract
Paleomagnetic information reconstructed from archeological materials can be utilized to estimate the archeological age of excavatedrelics, in addition to revealing the geomagnetic secular variation and core dynamics. The direction and intensity of the Earth’s
magnetic field (archeodirection and archeointensity) can be ascertained using different methods,
many of which have been proposed over the past decade. Among the new experimental techniques
for archeointensity estimates is the Tsunakawa–Shaw method. This study demonstrates the validityof the Tsunakawa–Shaw method to reconstruct archeointensity from samples of baked clay fromarcheological relics. The validity of the approach was tested by comparison with the IZZI-Thellier
method. The intensity values obtained coincided at the standard deviation (1σ) level. A total of 8
specimens for the Tsunakawa–Shaw method and 16 specimens for the IZZI-Thellier method, from 8
baked clay blocks, collected from the surface of the kiln were used in these experiments. Amongthem, 8 specimens (for the Tsunakawa–Shaw method) and 3 specimens (for the IZZI-Thellier
method) passed a set of strict selection criteria used in the final evaluation of validity. Additionally,
we performed rock magnetic experiments, mineral analysis, and paleodirection measurement toevaluate the suitability of the baked clay samples for paleointensity experiments and hence
confirmed that the sample properties were ideal for performing paleointensity experiments. It isnotable that the newly estimated archaomagnetic intensity values are lower than those in previous
studies that used other paleointensity methods for the tenth century in Japan.

Keywords: Archeointensity experiment, Sueki kiln in Japan, Tsunakawa–Shaw method

Graphical abstract*Corresponding author: Yu Kitahara, 3gs15005w@s.kyushu-u.ac.jp

FULL PAPER

Open Access

Rock magnetism of quartz and feldspars chemicallyseparated from pelagic red clay: a new approach toprovenance study
Yoichi Usui*, Takaya Shimono and Toshitsugu Yamazaki
Earth, Planets and Space 2018, 70:153 DOI: 10.1186/s40623-018-0918-1
Received: 8 May 2018, Accepted: 5 September 2018, Published: 26 September 2018

Abstract
Magnetic mineral inclusions in silicates are widespread in sediments as well as in igneous rocks. Because they are isolated from surrounding
environment, they have potential to preserve original magnetic signature even in chemically altered sediments. Such inclusions may provide
proxies to help differentiating the source of the host silicate. We measure magnetism of quartz and feldspars separated by chemical digestion of
pelagic red clay. The samples are from the upper 15 m of sediments recovered at Integrated Ocean Drilling Program Site U1366 in the South
Pacific Gyre. The quartz and feldspars account for 2.3–22.7 wt% of the samples. X-ray diffraction analyses detect both plagioclase feldspar andpotassium feldspar. Plagioclase is albite-rich and abundant in the top ~ 7.4 m of the core. Potassium feldspar mainly occurs below ~ 10.4 m. The
dominance of albite-rich plagioclase differs from a previous investigation of coarser fraction of sediments from the South Pacific. Saturation
isothermal remanence (SIRM) intensities of the quartz and feldspars are 7.45 × 10−4 to 1.98 × 10−3 Am2/kg, accounting for less than 1.02% of the
SIRM of the untreated bulk samples. The depth variations of the silicate mineralogy and the previously reported geochemical end-member
contributions indicate that quartz and/or plagioclase above 8.26 m is likely to be Australian dust. In contrast, the relative abundance and themagnetic properties of quartz and feldspars vary below 10.42 m, without clear correlation with geochemical end-member contributions. We
consider that these changes trace a subdivision of the
volcanic component. Our results demonstrate thatmagnetism of inclusions can reveal additional
information of mineral provenance, and chemical
separation is an essential approach to reveal theenvironmental magnetic information carried bymagnetic inclusions.

Keywords: Magnetic inclusions, South Pacific Gyre,
Eolian dust, Environmental magnetism

Graphical abstract*Corresponding author: Yoichi Usui, yoichi@jamstec.go.jp
6Earth, Planets and Space

FULL PAPER

Open AccessAn initial case study to deconvolve natural remanent
magnetization of a continuous paleomagnetic sample
using the software UDECON
Yuhji Yamamoto*, Toshitsugu Yamazaki and Toshiya Kanamatsu
Earth, Planets and Space 2018, 70:160 DOI: 10.1186/s40623-018-0931-4
Received: 14 June 2018, Accepted: 30 August 2018, Published: 1 October 2018

Abstract

relative depth [cm]Previous studies have compiled relative paleointensity data for the last 2–3 Ma from individual paleomagnetic records obtained from marine
sediment cores. These records have mostly been obtained by pass-through measurements, which are known to smooth and alter magnetic
signals. Among many efforts, a standalone open-use graphical software UDECON has been developed to deconvolve pass-throughmeasurement data. As an initial case study to assess the applicability of the software to deconvolve natural remanent magnetization (NRM) of
a continuous paleomagnetic sample, we chose 40 discrete samples from a piston core recovered in the northeast Pacific. We measured NRMs
after alternating field demagnetization at 20 mT for both discrete samples and a simulated continuous sample, made by connecting thediscrete samples. The discrete samples show centimeter-scalevariations in NRM. Such variations are smoothed out and mostly0
disappear in the results of the simulated continuous sample.
u-channel
However, after using the software to deconvolve the data, the20variations are almost completely restored. Good agreement
between the discrete sample data and the deconvolved data
discrete
discretedeconvolved
u-channel
indicates that the deconvolution by the software is very successful.
40
We observe detailed features of a directional reversal in the data
deconvolved
u-channel (x 1.36)
discretefrom the discrete samples and in the deconvolved data but not in
60
deconvolved (x 1.04)
the data from the simulated continuous sample. This emphasizes
that the deconvolution analysis by the software is a powerful tool80
to extract detailed features from continuous paleomagnetic
records obtained by pass-through measurements.
1000

Keywords: Superconducting rock magnetometer,

2 10

-5

-5

4 10

-5

6 10

-5

8 10

NRM Intensity 20mT [A/m]

-90

-60

-30

0

30

60

90

-90

Inclination 20mT [deg]

0

90

180

270

relative Declination 20mT [deg]Graphical abstract

Deconvolution, Reversal*Corresponding author: Yuhji Yamamoto, y.yamamoto@kochi-u.ac.jp

FULL PAPER

Open AccessRemanence cycling of 0.6–135 µm magnetites acrossthe Verwey transition
David J. Dunlop* and Özden ÖzdemirEarth, Planets and Space 2018, 70:164 DOI: 10.1186/s40623-018-0928-z
Received: 11 July 2018, Accepted: 18 September 2018, Published: 4 October 2018

Abstract
We report zero-field low-temperature cycling of saturation remanence (SIRM) produced at 300 or 10 K for crushed natural
magnetites in nine size fractions from 0.6 to 135 µm, one set annealed to reduce stress, the other unannealed. Coercivities ofisothermal remanence increase tenfold between 300 and 10 K, possibly explaining an apparent transition near 50 K. 300-K SIRM
decreases continuously on cooling, losing 60–80% by TV = 120 K (Verwey transition), is constant from 120 to 10 K, then recovers asmall memory in warming through TV to 300 K. A dip and recovery of remanence near TV for larger (> 15 µm) annealed grains isprobably due to memory of cubic domain structures by monoclinic
0
50
100
150
200
250
300
magnetite below TV, permitting partial recovery of initial remanence.
1.0
1.0
M/M
o
In warming, 10-K SIRM is little affected until lost catastrophically near
TV. A small memory is recovered in cooling to 10 K. The contrasting
0.8
0.8
behaviors of 300-K and 10-K SIRMs result from the contrasting
anisotropies and domain structures of cubic and monoclinic
0.6
0.6
magnetite. Memories of initial remanences after full temperature
1 μm
cycles are attributed to monoclinic magnetite providing a template
0.4
0.4
6 μm
1 μm
for partially regenerating initial cubic domain structures on the
6 μm
9 μm
second passage through TV. Memory ratios as a function of grain size
9 μm
0.2
0.2
14 μm
for our magnetites are too scattered to be granulometrically useful.
14 μ m

Keywords: Magnetite, Verwey transition, Saturation remanence,
Low-temperature cycling

0
0

50

100

150

Temperature, T (K)Graphical abstract*Corresponding author: David J. Dunlop, dunlop@physics.utoronto.ca
7

200

250

0
300

Recent Advances in Geo-, Paleo- and Rock- Magnetism

FULL PAPER

Open AccessPossible correlation between the vertical component oflithospheric magnetic field and continental seismicity
Yu Lei, Liguo Jiao* and Huaran Chen
Earth, Planets and Space 2018, 70:179 DOI: 10.1186/s40623-018-0949-7
Received: 8 April 2018, Accepted: 1 November 2018, Published: 16 November 2018

Abstract
Recent magnetic satellite missions facilitate new birth of large-scale
geomagnetic field models and their applications to tectonics. Here, we directlycompare the global geomagnetic field models NGDC-720 with the tectonics
and seismicity in Mainland China and surroundings. It is found that thetectonics and seismicity in this area show remarkable correlation with thevertical component of lithospheric magnetic field (Bz) calculated at an altitudeof 200 km. Previous thought was that earthquakes are more likely to occur inzero Bz belts or in obvious anomaly gradient belts. On the contrary, we findthat more than half (53.2%) of the earthquakes occurred in areas with Bz of − 5
to − 3 nT or in areas with a relatively small horizontal gradient of Bz in the sametime interval with the satellite data. The percentage seismic energy in theseareas (− 5 nT < Bz < − 3 nT) is even as high as 94.6%. We explain this unexpected
result with a two equivalent source dipole model, arguing that the viscosity
difference caused by the temperature gradient within the lithosphere likely
accounts for the correlation between magnetic anomalies and seismicity.

Keywords: Lithosphere magnetic field, Satellite, Tectonics, Continental
seismicity, Mainland China

Graphical abstract*Corresponding author: Liguo Jiao, lgjiao@cea-igp.ac.cn

FULL PAPER

Open Access

Near-seafloor magnetic mapping of off-axis lava flows near
the Kairei and Yokoniwa hydrothermal vent fields in
the Central Indian Ridge
Masakazu Fujii* and Kyoko Okino
Earth, Planets and Space 2018, 70:188 DOI: 10.1186/s40623-018-0959-5
Received: 17 April 2018, Accepted: 13 November 2018, Published: 4 December 2018

Abstract
The Kairei (KHF) and Yokoniwa hydrothermal fields (YHF) are hosted in mafic as well as ultramafic rocks distributed at an off-axis volcanic knoll of
the Central Indian Ridge. Despite intensive investigations, their geological and geophysical background is still debated. Here, we show the resultsof near-seafloor magnetic anomaly surveys conducted using a submersible. We investigated the bulk magnetization of the hydrothermallyaltered zone and the surrounding lava flows and evaluated their intensities compared with previously reported values at axial areas of seafloor
spreading environments. The KHF is characterized by low coherence between observed and modeled
anomalies and low values of magnetization. This result suggests that magnetic minerals within basaltic
lava flows were likely altered by hydrothermal fluid circulation. The variation pattern in the observed
magnetic anomalies above the lava flows is in phase with that of the modeled magnetic anomalies forthe simple assumption that the magnetization direction is parallel to the geomagnetic field. This result
suggests that these lava flows preserve normal magnetic polarity corresponding to the Brunhes Chron.
The estimated magnetic-anomaly-derived absolute magnetizations show a reasonable correlation with
the natural remanent magnetizations of rock samples collected from the seafloor of the same region;
their relationship is consistent with previously reported datasets from the Mariana Trough and MidAtlantic Ridge. The estimated magnetization intensity reaches 20 A/m in the study area, which is clearly
greater than those of previously reported off-axis areas, suggesting that recent volcanic eruption may
have occurred in these off-axis areas. The high magnetization distributions are commonly observed at
the bottoms of the western slope from the KHF and YHF. This finding provides new insight into the
distribution of highly magnetized lava flows in the off-axis areas and indicates the distribution of recent
off-axis volcanic activities, which is potentially linked to the sub-seafloor hydrothermal circulation.

Keywords: Seafloor hydrothermal system, Marine magnetic anomaly, Off-axis lava flow, Central Indian
Ridge, Kairei site, Yokoniwa site

*Corresponding author: Masakazu Fujii, fujii.masakazu@nipr.ac.jp
8Graphical abstract

Earth, Planets and Space

FULL PAPER

Open AccessSeafloor hydrothermal alteration affecting magnetic propertiesof abyssal basaltic rocks: insights from back-arc lavas of
the Okinawa Trough
Masakazu Fujii*, Hiroshi Sato, Eri Togawa, Kazuhiko Shimada and Jun-ichiro Ishibashi
Earth, Planets and Space 2018, 70:196 DOI: 10.1186/s40623-018-0958-6
Received: 7 April 2018, Accepted: 13 November 2018, Published: 13 December 2018

Abstract
Seafloor hydrothermal systems in the back-arc region of the Okinawa Trough have been viewed as a modern analogue to the Kuroko-type
volcanogenic massive sulfide deposits. Detection of magnetic signatures is widely utilized and assumed to facilitate the understanding ofgeological controls on hydrothermal system genesis. However, the magnetic properties of seafloor volcanic rocks are still poorly understoodbecause of the difficulties of sample acquisition. Here, we report rock magnetic data along with linked geochemical and petrological data of
volcanic rock samples obtained from the Irabu knolls of the southern Okinawa Trough. Both fresh and hydrothermally altered basaltic andesites
were successfully obtained from the seafloor via submersible. A fresh sample, with single-domain titanomagnetite grains, is strongly magnetizedwith NRM intensity of up to 100 A/m. Minute skeletal and dendritic titanomagnetite grains are also observed. A second fresh sample, with multidomain titanomagnetite grains, contains a greater amount of titanomagnetite grains, but exhibits NRM intensity ~ 10 A/m at most. In contrast to
the fresh samples, hydrothermally altered samples show extremely low NRM intensities along with low saturation magnetization and certain
contribution of paramagnetic minerals. Grain assemblages of pyrite and chalcopyrite grains appear along cracks in the groundmass. Our results
indicated that fine titanomagnetite grains in groundmass within back-arc lava flows are altered due to hydrothermal processes. The recorded
primary remanent magnetization of the lava flows is thus partly removed byhydrothermal alteration. Magnetization reduction related to hydrothermal
activity produces local crustal magnetization lows and thus enables us to detect
hydrothermal alteration zones by utilizing magnetic field measurements inspace. In particular, the lavas we examined (via their resultant basaltic andesites)
have high Curie temperatures greater than 400 °C, which is significantly higher
than those indicated by mid-ocean ridge basalts, suggesting that the thermal
effect for crustal magnetization may be less in back-arc settings.

Keywords: Magnetic properties, Hydrothermal alteration, Titanomagnetite,
Back-arc basaltic andesite, Okinawa TroughGraphical abstract*Corresponding author: Masakazu Fujii, fujii.masakazu@nipr.ac.jp

FULL PAPER

Open Access

The effects of dislocations on crystallographic twins anddomain wall motion in magnetite at the Verwey transition
Anna K. Lindquist*, Joshua M. Feinberg, Richard J. Harrison, James C. Loudon and Andrew J. Newell
Earth, Planets and Space 2019, 71:5 DOI: 10.1186/s40623-018-0981-7
Received: 15 August 2018, Accepted: 24 December 2018, Published: 15 January 2019

Abstract
Pure magnetite experiences a first-order phase transition (the Verwey transition) near 120–125 K wherein the mineral’s symmetry changes fromcubic to monoclinic. This transformation results in the formation of fine-scale crystallographic twins and is accompanied by a profound change inmagnetic properties. The Verwey transition is critical to a variety of applications in environmental magnetism and paleomagnetism because its
expression is diagnostic for the presence of stoichiometric (or nearly stoichiometric)
magnetite and cycling through the Verwey transition tends to remove the majority ofmultidomain magnetic remanence. Internal and external stresses demonstrably affect theonset of the Verwey transition. Dislocations create localized internal stress fields and havebeen cited as a possible source of an altered Verwey transition in deformed samples. To
further investigate this behavior, a laboratory-deformed magnetite sample was examinedinside a transmission electron microscope as it was cooled through the Verwey transition.
Operating the microscope in the Fresnel mode of Lorentz microscopy enabled imaging of
the interactions between dislocations, magnetic domain walls, and low-temperature
crystallographic twin formation during the phase transition. To relate the observedchanges to more readily measurable bulk sample magnetic behavior, low-temperaturemagnetic measurements were also taken using SQUID magnetometry. This study allows
us, for the first time, to observe the Verwey transition in a defect-rich area. Dislocations,and their associated stress fields, impede the development of monoclinic magnetite twin
structures during the phase transition and increase the remanence of a magnetite sample
after cooling and warming through the Verwey transition.

Keywords: Verwey transition, Magnetite, Dislocations, Domain wall, Transmission

electron microscopy, TEM, Low-temperature demagnetization, Oxidation,
Phase transition*Corresponding author: Anna K. Lindquist, alindqu1@macalester.edu
9Graphical abstract

Recent Advances in Geo-, Paleo- and Rock- Magnetism

FULL PAPER

Open AccessUsing TNT-NN to unlock the fast full spatial inversion oflarge magnetic microscopy data sets
Joseph M. Myre*, Ioan Lascu, Eduardo A. Lima, Joshua M. Feinberg, Martin O. Saarand Benjamin P. Weiss
Earth, Planets and Space 2019, 71:14 DOI: 10.1186/s40623-019-0988-8
Received: 11 August 2018, Accepted: 10 January 2019, Published: 4 February 2019

Abstract
Modern magnetic microscopy (MM) provides high-resolution, ultra-high-sensitivity moment magnetometry, with the ability to measure at spatial
resolutions better than 10−4 m and to detect magnetic moments weaker than 10−15 Am2. These characteristics make modern MM devices capable ofparticularly high-resolution analysis of the magnetic properties of materials, but generate extremely large data sets. Many studies utilizing MM
attempt to solve an inverse problem to determine the magnitude of the magnetic moments that produce the measured component of themagnetic field. Fast Fourier techniques in the frequency domain and non-negative least-squares (NNLS) methods in the spatial domain are the twomost frequently used methods to solve this inverse problem. Although extremely fast, Fourier techniques can produce solutions that violate thenon-negativity of moments constraint. Inversions in the spatial domain do not violate non-negativity constraints, but the execution times ofstandard NNLS solvers (the Lawson and Hanson method and Matlab’s lsqlin) prohibit spatial domain inversions from operating at the full spatial
resolution of an MM. In this paper, we present the applicability of the TNT-NN algorithm, a newly developed NNLS active set method, as a means to
directly address the NNLS routine hindering existing spatial domain inversion methods. The TNT-NN algorithm enhances the performance of
spatial domain inversions by accelerating the core NNLS routine. Using a conventional
computing system, we show that the TNT-NN algorithm produces solutions with residuals
comparable to conventional methods while reducing execution time of spatial domain
inversions from months to hours or less. Using isothermal remanent magnetization
measurements of multiple synthetic and natural samples, we show that the capabilities of
the TNT-NN algorithm allow scans with sizes that made them previously inaccesible to NNLS
techniques to be inverted. Ultimately, the TNT-NN algorithm enables spatial domain
inversions of MM data on an accelerated timescale that renders spatial domain analyses formodern MM studies practical. In particular, this new technique enables MM experimentsthat would have required an impractical amount of inversion time such as high-resolution
stepwise magnetization and demagnetization and 3-dimensional inversions.

Keywords: Magnetic microscopy, Rock magnetism, Non-negative least-squares

Graphical abstract*Corresponding author: Joseph M. Myre, myre@stthomas.edu

FULL PAPER

Open Access

Investigation of regional variation in core flow models
using spherical Slepian functions
Hannah F. Rogers*, Ciarán D. Beggan and Kathryn A. Whaler
Earth, Planets and Space 2019, 71:19 DOI: 10.1186/s40623-019-0997-7
Received: 16 June 2018, Accepted: 1 February 2019, Published: 18 February 2019

Abstract
By assuming that changes in the magnetic field in the Earth’s outer core are advection-dominated on short timescales, models of
the core surface flow can be deduced from secular variation. Such models are known to be under-determined and thus require
other assumptions to produce feasible flows. There are regions where poor knowledge of the core flow dynamics gives rise tofurther uncertainty, such as within the tangent cylinder, and assumptions about the nature of the flow may lead to ambiguous
patches, such as if it is assumed to be strongly tangentially geostrophic. We use spherical Slepian functions to spatially andspectrally separate core flow models, confining the flow to either inside or outside these regions of interest. In each region we
examine the properties of the flow and analyze its contribution to the overall model. We use three forms of flow model: (a)synthetic models from randomly generated coefficients with blue, red andwhite energy spectra, (b) a snapshot of a numerical geodynamo
simulation and (c) a model inverted from satellite magnetic fieldmeasurements. We find that the Slepian decomposition generates
unwanted spatial leakage which partially obscures flow in the region ofinterest, particularly along the boundaries. Possible reasons for this include
the use of spherical Slepian functions to decompose a scalar quantity thatis then differentiated to give the vector function of interest, and thespectral frequency content of the models. These results will guide
subsequent investigation of flow within localized regions, including
x 10
applying vector Slepian decomposition methods.

5

Keywords: Spherical Slepian functions, Outer core flow, Geostrophic flows,
Tangent cylinder

-8

-6

-4

-2

0

Fig. 1*Corresponding author: Hannah F. Rogers, h.f.rogers@sms.ed.ac.uk
102

Values of Br /cos θ (nT)

4

6

8

Earth, Planets and Space

EXPRESS LETTER

Open Access

Characterization of marine ferromanganese crust fromthe Pacific using residues of selective chemical leaching:identification of fossil magnetotactic bacteria with
FE-SEM and rock magnetic methods
Hirokuni Oda*, Yoshio Nakasato and Akira Usui
Earth, Planets and Space 2018, 70:165 DOI: 10.1186/s40623-018-0924-3
Received:2 August 2018, Accepted: 15 September 2018, Published: 5 October 2018

Abstract
Hydrogenetic ferromanganese crusts (hereafter referred to as “crusts”) on Pacific seamounts are formed by the precipitation of iron–manganeseoxides from seawater on volcanic and biogenic substrate rocks. As crusts grow continuously and have very slow growth rates of between 1 and
10 mm/m.y., they can potentially be used as records of the Neogene paleoceanographic and paleoclimatic conditions. Crusts can be considered
as compressed sediment cores containing biogenic, volcanogenic, and terrestrial particles that include eolian dusts and the partly weatheredproducts of substrate acquired during its growth. In this study, selective leaching experiments were conducted on a sample of ferromanganesecrust, which had been obtained from the Federated States of Micronesia at a water depth of 2262 m. Chemical leaching experiments wereconducted using oxalic acid buffered with ammonium oxalate on the crushed crust samples, which is an optimization of previously proposedsequential leaching procedures. The applied method was found to be effective in separating the major
mineral phases of crusts from associated metallic components, thereby providing concentration of theresidual fraction for use in analysis following the leaching experiment. Using this method, polygenetic
particles were extracted from the crust and identified using optical and electron microscopes. They were
found to be of various origins and included volcanogenic, biogenic, terrestrial, and extraterrestrial
material. In addition, well-sorted prism-shaped chained magnetic particles were observed in residual
fractions. Rock magnetic experiments support the idea that the magnetic particles are magnetites andoriginated from fossil magnetotactic bacteria. The fossil magnetotactic bacteria might have been living on
the crust at the time of crust formation. Alternatively, fossil magnetotactic bacteria could have beentransported by deep sea currents from the sediment where magnetotactic bacteria originated.

Keywords: Ferromanganese crust, Magnetotactic bacteria, Terrestrial, Extraterrestrial, Eolian, Cosmic
spherule, Titanomagnetite, Chemical leaching, Rock magnetism

Graphical abstract*Corresponding author: Hirokuni Oda, hirokuni-oda@aist.go.jp

TECHNICAL REPORT

Open Access

Online plotting applications for paleomagnetic androck magnetic data
Tadahiro Hatakeyama
Earth, Planets and Space 2018, 70:139 DOI: 10.1186/s40623-018-0906-5
Received: 5 April 2018, Accepted: 10 August 2018, Published: 23 August 2018

Abstract
This paper describes the development and releaseof a series of web-based services to generate plotsof paleomagnetic and rock magnetic data. All
plotting services require a World Wide Web browser
as the user interface. The use of online plotting
services facilitates rapid and easy sharing of work ofanalysis and preliminary results with collaborators
who use different platforms and operating systems.
To implement these routines, two paleomagnetic
data types (stepwise demagnetization andpaleodirection) are formally defined. These havebeen popular among researchers for many decades.

Keywords: Paleomagnetism, Rock magnetism,

Drawing applications, Online services

Graphical abstract

Corresponding author: Tadahiro Hatakeyama, hatake@center.ous.ac.jp
11

Recent Advances in Geo-, Paleo- and Rock- Magnetism

TECHNICAL REPORT

Open Access

Reductive chemical demagnetization: a new approach tomagnetic cleaning and a case study of reef limestones
Chisato Anai*, Nobutatsu Mochizuki and Hidetoshi Shibuya
Earth, Planets and Space 2018, 70:184 DOI: 10.1186/s40623-018-0954-x
Received: 15 April 2018, Accepted: 12 November 2018, Published: 26 November 2018

Abstract
Chemical demagnetization is not preferred as a demagnetizing method in paleomagnetism because strong acids are cumbersome to handle
and require considerable time compared to alternating field and thermal demagnetizations. Particularly, for rocks with carbonate minerals,
strong acidic solutions are not applicable. This study presents a new method, termed reductive chemical demagnetization (RCD), using
ascorbic acid solution as a reductive etchant. Ascorbic acid is a strong reductive agent and converts Fe3+ ions of secondary magnetic minerals
to water-soluble Fe2+ ions, which facilitate chemical demagnetization of carbonate rocks. The carbonate frame can remain intact if the pH of
the solution is buffered at approximately 7 with sodium bicarbonate. This etchant is more suitable than strong acid in terms of handling in apaleomagnetic laboratory, particularly in a magnetic field free room. To reduce the required time, a technique of dripping the etchant on thesample was also devised. This helps the fresh etchant flow through the voids between the grains of rocks to rapidly remove dissolved Fe2+
ions. As a case study of RCD, reef limestone samples were examined. The results showed that the dripping experiments with 5% ascorbic acidsolution were the most effective. It took 72 h to reach the remaining isothermal remanent magnetization (IRM) constant. Thermal
demagnetizations of 3-component IRM indicate that RCD removed thehigh coercivity remanences carried by hematite and goethite. Theseabmagnetic minerals were considered to be precipitated between the grainsof the rock, and thus they were dissolved by the RCD treatment. A
chemical remanent magnetization (CRM), acquired by secondary magnetic
minerals, can easily mask the primary remanence for sedimentary rocks of
weak magnetization, and the coercivity or unblocking-temperature
spectra of the primary remanence and secondary CRM overlap; however,
RCD can effectively remove the secondary CRM. RCD prior to alternating
field or thermal demagnetization has the potential to improve
paleomagnetic demagnetization of sedimentary rocks.

Keywords: Reductive chemical demagnetization, Reductive etchant,
Ascorbic acid, Reef limestone*Corresponding author: Chisato Anai, chisato@kumamoto-u.ac.jp

12Graphical
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Contents
Special issue “Recent advances in geo-, paleo- and rock-magnetism”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . John A. Tarduno, Hirokuni Oda, Yuhji Yamamoto, Chuang Xuan, Ioan Lascu and Koji Fukuma
Paleomagnetic studies on single crystals separated from the middle Cretaceous Iritono granite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chie Kato, Masahiko Sato, Yuhji Yamamoto, Hideo Tsunakawa and Joseph L. Kirschvink
Constraining the magnetic properties of ultrafine- and fine-grained biogenic magnetite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tongwei Zhang and Yongxin Pan
A paleomagnetic record in loess–paleosol sequences since late Pleistocene in the arid Central Asia
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Guanhua Li, Dunsheng Xia, Erwin Appel, Youjun Wang, Jia Jia and Xiaoqiang Yang
Preliminary paleomagnetic and rock magnetic results from 17 to 22 ka sediment of Jeju Island, Korea:
Geomagnetic excursional behavior or rock magnetic anomalies?
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hyeon-Seon Ahn, Young Kwan Sohn, Jin-Young Lee and Jin Cheul Kim
Archeointensity estimates of a tenth-century kiln: first application of the Tsunakawa–Shaw paleointensity method toarcheological relics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Yu Kitahara, Yuhji Yamamoto, Masao Ohno, Yoshihiro Kuwahara,
Shuichi Kameda and Tadahiro Hatakeyama

Rock magnetism of quartz and feldspars chemically separated from pelagic red clay: a new approach to provenancestudy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Yoichi Usui, Takaya Shimono and Toshitsugu Yamazaki
An initial case study to deconvolve natural remanent magnetization of a continuous paleomagnetic sample using
the software UDECON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Yuhji Yamamoto, Toshitsugu Yamazaki and Toshiya Kanamatsu
Remanence cycling of 0.6–135 µm magnetites across the Verwey transition. . . . . . . . . . . . . David J. Dunlop and Özden Özdemir
Possible correlation between the vertical component of lithospheric magnetic field and continental seismicity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Yu Lei, Liguo Jiao and Huaran Chen
Near-seafloor magnetic mapping of off-axis lava flows near the Kairei and Yokoniwa hydrothermal vent fields in
the Central Indian Ridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Masakazu Fujii and Kyoko Okino
Seafloor hydrothermal alteration affecting magnetic properties of abyssal basaltic rocks: insights from back-arc lavasof the Okinawa Trough . . . . . . . . . . . . . . . . . . . . . . Masakazu Fujii, Hiroshi Sato, Eri Togawa, Kazuhiko Shimada and Jun-ichiro Ishibashi
The effects of dislocations on crystallographic twins and domain wall motion in magnetite at the Verwey transition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anna K. Lindquist, Joshua M. Feinberg, Richard J. Harrison, James C. Loudon and Andrew J. Newell
Using TNT-NN to unlock the fast full spatial inversion of large magnetic microscopy data sets
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Joseph M. Myre, Ioan Lascu, Eduardo A. Lima, Joshua M. Feinberg, Martin O. Saar and Benjamin P. Weiss
Investigation of regional variation in core flow models using spherical Slepian functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hannah F. Rogers, Ciarán D. Beggan and Kathryn A. Whaler
Characterization of marine ferromanganese crust from the Pacific using residues of selective chemical leaching:identification of fossil magnetotactic bacteria with FE-SEM and rock magnetic methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hirokuni Oda, Yoshio Nakasato and Akira Usui
Online plotting applications for paleomagnetic and rock magnetic data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tadahiro Hatakeyama
Reductive chemical demagnetization: a new approach to magnetic cleaning and a case study of reef limestones. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chisato Anai, Nobutatsu Mochizuki and Hidetoshi Shibuya

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Cover image: Fujii, M. et al., Earth, Planets and Space 2018, 70:188 DOI: 10.1186/s40623-018-0959-5